Implementation of a spreadsheet program for calculation of equivalent square field size.

Equivalent square field size is a parameter widely used in calculations for external beam treatment planning. The algorithm and features of a spreadsheet program used to calculate the equivalent square, independently of the treatment planning system, are described. The program uses an approximation method based on the application of Lamé curves.

Design of a multiblock phantom for radiotherapy dosimetry applications.

This note describes the design of a multiblock semi-anatomic phantom, which lends itself to a variety of radiotherapy dosimetry applications, in particular, the audit of external beam treatment planning and delivery. The basic building blocks of the phantom were formed from a variety of tissue substitute materials and could be assembled in many ways to model different cross-sections through the body.

Use of Monte Carlo computation in benchmarking radiotherapy treatment planning system algorithms.

Radiotherapy treatments are becoming more complex, often requiring the dose to be calculated in three dimensions and sometimes involving the application of non-coplanar beams. The ability of treatment planning systems to accurately calculate dose under a range of these and other irradiation conditions requires evaluation. Practical assessment of such arrangements can be problematical, especially when a heterogeneous medium is used.

Assessment of background hydrogen by the Monte Carlo computer code MCNP-4A during measurements of total body nitrogen.

The use of a hydrogen internal standard to enable the estimation of absolute mass during measurement of total body nitrogen by in vivo neutron activation is an established technique. Central to the technique is a determination of the H prompt gamma ray counts arising from the subject. In practice, interference counts from other sources--e.

An MCNP-based model of a linear accelerator x-ray beam.

The Monte Carlo N-Particle radiation transport computer code (MCNP) has been employed on a personal computer to develop a simple model simulating the major components within the beam path of a linear accelerator radiation head, namely the electron target, primary conical collimator, beam flattening filter, wedge filter and the secondary collimators. The model was initially used to calculate the energy spectra and angular distributions of the x-ray beam for the Philips SL 75/5 linear accelerator, in a plane immediately beneath the flattening filter. These data were subsequently used as a 'source' of x-rays at the target position, to assess the emergent beam from the secondary collimators.

Benchmarking the MCNP code for Monte Carlo modelling of an in vivo neutron activation analysis system.

The Monte Carlo computer code MCNP (version 4A) has been used to develop a personal computer-based model of the Swansea in vivo neutron activation analysis (IVNAA) system. The model included specification of the neutron source (252Cf), collimators, reflectors and shielding. The MCNP model was 'benchmarked' against fast neutron and thermal neutron fluence data obtained experimentally from the IVNAA system.

Monte Carlo simulation of prompt gamma neutron activation analysis using MCNP code.

Prompt gamma neutron activation analysis (PGNAA) is the most direct method of measuring total-body nitrogen. In combination with internal hydrogen standardisation, it is possible to reduce the dependence on body habitus. The uniformity of activation and detection, however, cannot be optimised sufficiently to eliminate the dependence entirely, and so further corrections are essential.

Changes in body fat: measurements by neutron activation, densitometry and dual energy X-ray absorptiometry.

The measurement of body fat in ten subjects (BMI from 22 to 43 kg/m2), and in particular the changes arising from a ketogenic diet, by the techniques of in vivo neutron activation analysis (NAA), densitometry (using two- and four-compartment models) by under water weighing (UWW) and dual energy X-ray absorptiometry (DXA) was compared. The association between techniques for the fat changes was generally high (r = 0.70 to 0.

The performance of an infra-red interactance instrument for assessing total body fat.

Infra-red interactance has been evaluated as a technique for measuring total body fat in comparison with a range of alternative methods. The alternative techniques employed were neutron activation analysis, tritiated water dilution, whole-body potassium-40 counting, skinfold anthropometry, bioelectrical impedance analysis and the body mass index. The study group consisted of 43 healthy adults (16 males and 27 females).

Monte Carlo design study of a moderated 252Cf source for in vivo neutron activation analysis of aluminium.

The Monte Carlo computer code MCNP has been used to design a moderated 252Cf neutron source for in vivo neutron activation analysis of aluminium (Al) in the bones of the hand. The clinical motivation is the need to monitor Al body burden in subjects with renal dysfunction, at risk of Al toxicity. The design involves the source positioned on the central axis at one end of a cylindrical deuterium oxide moderator.

Absolute measurements of total-body calcium using prompt gamma neutron analysis and internal chlorine standardization: results in renal patients.

Measurement of total-body calcium (TBCa) is important in the study of several medical conditions. Neutron activation analysis (NAA) is sufficiently precise for serial measurements, but in order to provide single, absolute determinations of TBCa, it requires a correction for body habitus. A method is described for the absolute determination of TBCa by comparing the total-body chlorine, obtained by NAA, with that obtained by stable bromine dilution.

The effect of oestradiol implants on regional and total bone mass: a three-year longitudinal study.

Objective: Although there is evidence from cross-sectional studies that percutaneous oestrogen administration protects against menopausal bone loss, few longitudinal data are available. We have examined the effect of 3 years' treatment with percutaneous oestradiol on total body calcium, spinal trabecular bone mineral density and radial bone mineral content in post-menopausal women.

Design And Patients: Twenty-nine post-menopausal women, aged 37-55 years, who had undergone hysterectomy and had experienced the onset of menopausal symptoms within the previous 2 years, were studied before and for 3 years during hormone replacement with oestradiol implants, given at approximately 6-monthly intervals.

A five-compartment model of body composition of healthy subjects assessed using in vivo neutron activation analysis.

A body composition study of 31 healthy subjects covering a wide range of age (23.5-72.0 years) and weight (44.

The development of a technique to measure bone aluminium content using neutron activation analysis.

The accumulation and toxicity of aluminium in patients with chronic renal failure is a well recognized hazard, and there is a need for a non-invasive technique to assess Al tissue load in these patients. The technique of in vivo neutron activation analysis, using a thermal neutron beam from a reactor, has been employed by previous workers, who measured Al in the hand with a detection limit of 0.4 mg for a dose equivalent of 20 mSv.

The composition of weight loss in dieting obese females by electrical methods.

The fat and fat-free components of the weight loss of a group of obese females undergoing a clinically monitored dieting regime have been estimated by two noninvasive electrical techniques, bioelectrical impedance analysis (BIA) and tissue resonance impedance monitoring (TRIM). These two procedures are described and results presented for a group of volunteers representing a wide range of body mass index. During the 11 weeks of the study the members of the group were on a 405 kcal liquid ketogenic diet.

The measurement of silicon in a lung phantom--a comparison of two nuclear reactions for in vivo activation analysis.

The amount of silica in the human lung may be estimated by measurement of silicon using in vivo neutron activation analysis. A pulsed, fast neutron beam, produced with a 2 MV Van de Graaff generator using the 2H + 2H reaction, was used to irradiate a Si-doped chest phantom in order to determine minimum detection limits (MDL). Two 'in-beam' nuclear reactions on Si were studied; prompt fast neutron inelastic scatter 28Si (n,n' gamma)28Si reaction was measured during the beam burst and the slow neutron prompt capture reaction was measured between the fast neutron bursts.

Changes in total body nitrogen during weight reduction by very-low-calorie diets.

Body composition measurements, including total body nitrogen (TBN) by in vivo neutron activation analysis, were made on 11 female volunteers before and after an 11-wk very-low-calorie diet (VLCD) [1695 kJ (405 kcal) 6.7 g N]. Mean body mass index (BMI) changed from 32.

Dependence of weight loss during very-low-calorie diets on total energy expenditure rather than on resting metabolic rate, which is associated with fat-free mass.

The assumption that total energy expended is related to resting metabolic rate (RMR) has not been validated. Intuitively, weight lost should be determined by the difference between the total energy consumed and the total energy expended. The ratio of actual daily energy usage to RMR by subjects dieting for 11 wk on a 1695-kJ (405-kcal) very-low-calorie diet (VLCD) was variable 1.

Total body calcium in patients with inflammatory bowel disease: a longitudinal study.

1. Serial measurements of total body calcium have been made by prompt gamma-neutron activation analysis in 13 patients with inflammatory bowel disease over a mean period of 23 months. Changes in spinal trabecular bone mineral density and radial shaft bone mineral content were also assessed by using quantitative computed tomography and single photon absorptiometry, respectively.

Measurements of total body calcium by prompt-gamma neutron activation analysis using a 252Cf source.

A clinical neutron activation instrument has been developed for in vivo elemental analysis. Utilizing the prompt-capture gamma ray technique, simultaneous total body (TB) measurements of primarily Ca, but also Cl, N, C, and H are routinely performed. This paper describes a technique for the measurement of TBCa (g) that relies on the use of TBCl as an internal standard.